Overhead electric power lines, wires or conductors are supported by poles or towers which may be constructed of wood, metal or other common materials. The overhead power lines are mounted on the poles or towers by insulators which are maintained upright by an upstanding pin engaging an axial blind bore of the insulator body.
These insulators were, in the past, typically constructed of a ceramic material such as porcelain, and have a variety of shapes and/or designs depending upon the necessary mechanical strength, dielectric strength and leakage distance. However, the use of porcelain for insulators has several disadvantages. For example, porcelain insulators are often very heavy to provide the necessary mechanical and electrical characteristics. Moreover, such porcelain insulators are typically expensive to install and require strong supporting structures. Additionally, porcelain insulators are brittle which makes them subject to being damaged during shipping and installation. Porcelain insulators are also susceptible to vandalism damage.
Accordingly, in recent years, newer insulators have been developed which include a fiberglass reinforced polymer core and an external protective housing forming annular flanges or webbed weathersheds. The weathershed housing or sheath is usually made of an elastomeric or an epoxy material. Elastomer or epoxy sheaths are designed to protect the fiberglass reinforced rods from weather and electrical activity. Weather and electrical activity degrade the mechanical strength of the fiberglass reinforced rods. The weathersheds on the housing intercept water flow down the insulators and increase the distance along the surface of the insulator for better electrical performance in wet or contaminated conditions.
Examples of some prior electrical devices are disclosed in U.S. Pat. Nos.: 3,531,580 to Foster; 4,243,628 to Herold; 4,440,975 to Kaczerginski, 4,476,081 to Kaczerginski et al; 4,702,873 to Kaczerginski; 4,714,800 to Atkins et al; 4,749,824 to Orbeck; 4,940,857 to Giroux; 5,220,134 to Novel et al; 5,147,984 to Mazeika et al; 5,233,132 to Soucille; 5,298,301 to Midgley et al; 5,406,033 to Pazdirek. Another example of a prior electrical device is enclosed in German Patent no. 1,932,949 to Brown, Boveri & Cie.
Generally, the core material is less costly than the sheath material. Accordingly, these newer types of insulators which utilize an elastomer or an epoxy material for its sheath can sometimes be expensive to manufacture. Accordingly, there exists a need for an electrical insulator which minimizes the amount of sheath material used in manufacturing the insulator. This invention addresses this need in the prior art as well as other needs which will become apparent to those skilled in the art from this disclosure.